docs: def load_registry(self, fname):
          """
          Load entries from a file and add them to the registry.
  
          Use this if you are managing many files.
  
          Each line of the file should have file name and its SHA256 hash separate by a
          space. Only one file per line is allowed. Custom download URLs for individual
          files can be specified as a third element on the line.
  
          Parameters
          ----------
          fname : str
              File name and path to the registry file.
  
          """
          with open(fname) as fin:
              for linenum, line in enumerate(fin):
                  elements = line.strip().split()
                  if len(elements) > 3 or len(elements) < 2:
                      raise IOError(
                          "Expected 2 or 3 elements in line {} but got {}.".format(
                              linenum, len(elements)
                          )
                      )
                  file_name = elements[0]
                  file_sha256 = elements[1]
                  if len(elements) == 3:
                      file_url = elements[2]
                      self.urls[file_name] = file_url
                  self.registry[file_name] = file_sha256